Expanding Portable Peripheral Capabilities
The basic portable should, at a minimum, contain all the devices a user needs to perform work away from the office. Users have become accustomed to using additional items with their computers, however. For this reason, portable computers typically offer a full range of I/O port types. In addition, portable computer manufacturers have produced an extensive array of products that can be added to a basic portable system to enhance its performance.
A docking station, or docking port, is a specialized structure that permits the notebook unit to be inserted into it. When the notebook is inside, the docking port extends its expansion bus so that it can be used with a collection of desktop devices, such as an AC power source, a full-sized keyboard and CRT monitor, as well as modems, mice, and standard PC port connectors. Figure 3.21 depicts a typical docking station.
Figure 3.21 A docking station.
The notebook and the docking station communicate with each other through a special docking-port connector in the rear of the notebook. When the notebook is inserted into the docking station, its extension bus plugs into the expansion connector in the notebook. Most docking stations provide standard full-size expansion slots so that non-notebook peripheral devices, such as network adapters and sound cards, can be used with the system. Docking stations may also provide additional PCMCIA slots for the notebook computer. When the notebook is in the docking station, its normal I/O devices (keyboard, display, and pointing device) are normally disabled, and the docking station's peripherals take over.
Docking stations are proprietary to the portable computer they were designed to work with. The docking-port connection in the docking station must correctly align with the connector in the notebook. The notebook unit must also fit correctly within the docking-station opening. Because there are no standards for these systems, the chances of two different manufacturers locating the connectors in the same place and/or designing the same case outline are very small.
Many notebook computer manufacturers offer devices similar to docking stations that are called port replicators. These devices plug into the notebook computer and contain common PC ports such as serial and parallel ports. The purpose of these devices is to enable users to attach portable computers to standard, nonportable devices such as printers and monitors.
Notebook manufacturers typically offer port replicators as additional proprietary options for their computers. Although these systems are similar to docking stations, they do not provide the additional expansion slots for adding optional adapter cards and disk drives found in docking stations.